#include<iostream>
#include<vector>
#include<queue>
#include<cstring>
#include<cmath>
#include<map>
#include<set>
#include<cstdio>
#include<algorithm>
#define debug(a) cout<<#a<<"="<<a<<endl;
using namespace std;
const int maxn=2e5+1000;
typedef long long LL;
inline LL read(){LL x=0,f=1;char ch=getchar();	while (!isdigit(ch)){if (ch=='-') f=-1;ch=getchar();}while (isdigit(ch)){x=x*10+ch-48;ch=getchar();}
return x*f;}
LL up[maxn],down[maxn];
/*
1
7 437
27 43
94 99
100 100
60 67
37 98
39 58
80 100
*/
bool check(LL x,LL n,LL s){
    LL cost=0;
    vector< pair<LL,LL> >v;
    for(LL i=1;i<=n;i++){
        if(up[i]<x){
           cost+=down[i];
        }
        else v.push_back({down[i],i});
    }
    sort(v.begin(),v.end());
    LL num=(n+1)/2;
    if(v.size()<num) return false;

    for(LL i=0;i<v.size()-num;i++){
        cost+=down[v[i].second];
    }
    for(LL i=v.size()-num;i<v.size();i++){
        cost+=max(x,down[v[i].second]);
    }
    if(cost<=s) return true;
    else return false;
}
int main(void){
   LL t;t=read();
   while(t--){
      LL n;n=read();LL s;s=read();
      for(LL i=1;i<=n;i++){
          down[i]=read();up[i]=read();
      }
      LL l=1;LL r=s;
      while(l<r){
        LL mid=(l+r+1)>>1;
        if(check(mid,n,s)) l=mid;
        else r=mid-1;
      }
      printf("%lld\n",l);
   }
   return 0;
}

